China on Friday voiced hope that it will "move forward" to warmer relations with North Korea this year at a time when Pyongyang seeks to deepen its diplomatic ties with Russia.

China's relationship with its ally, but troublesome neighbor appears to have been self-contradicting, but Beijing's leadership has expressed a sense of frostiness in dealings with the North since Pyongyang's third nuclear test in February 2013.

In a sign that China seeks to mend fences with North Korea, however, Beijing sent a rare message of best wishes for this week's birthday of the North's young leader, Kim Jong-un.

"We hope that North Korea can follow the principle of pushing forward its traditional friendship and cooperation (with China) in keeping with the principles of carrying on the tradition, looking to the future, developing good-neighborly and friendly relations and enhancing cooperation so as to move forward China-North Korea relations," China's foreign ministry spokesman Hong Lei told reporters during a regular press briefing. 

The remarks by Hong are widely seen as stressing the principle of North Korea-China relations, which was approved by North Korea's late leader Kim Jong-il and then Chinese President Jiang Zemin in 2001. Over the past year, Chinese officials have not made comments to that effect.

Asked whether China would send high-level officials to North Korea this year, Hong replied, "As for the high-level exchanges, I have no relevant information to offer at the current stage."

Political ties between North Korea and China remain strained, particularly after the North's third nuclear test.

In what many analysts believe was a message to North Korea, Chinese President Xi Jinping paid a state visit to South Korea last year, breaking a long-standing tradition by Chinese heads of state of visiting Pyongyang before Seoul.

The congratulatory message by China on Kim's birthday also came as North Korea is trying to deepen its ties with Russia.

With international pressure mounting on North Korea for its nuclear program and dismal human rights record, the North's young leader sent his special envoy to Moscow late last year and the envoy met with Russian President Vladimir Putin.

Russia has also said that it invited Kim to Moscow in May this year to attend a ceremony marking the 70th anniversary of the victory over Nazi Germany.

Kim, who inherited power after the death of his father in late 2011, has yet to visit China. (Yonhap)